In the coming year experiments will continue using the "window method" to describe some of the actions of other surface charge agents on the Na ion current (including lidocaine and DPH). Use of the extracellular K ion electrode will also continue. Studies in the presence of the voltage clamp will analyze accumulation of K ion at various doses of the cardiac glycosides. Salicylate actions to alter this accumulation will also be analyzed. The role of (Kion) changes in arrythmias will also be pursued. Experiments on canine purkinje fibres in the presence of Kion electrodes will be performed to see if the period of supernormal excitability corresponds to a period of elevated cleft (Kion). Computing using models to simulate various aspects of the experimental projects will also be pursued.